Xml

XML
Anjali g
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MAIN POINTS
• What is XML
• Difference between XML and HTML
• How to use XML
• XML tree
• XML syntax
• XML elements and attributes
• Us e of xml

What is XML?
• XML stands for Extensible Markup Language
• XML is a markup language much like HTML
• XML was designed to carry data, not to display data
• XML tags are not predefined. You must define your own tags
• XML is designed to be self-descriptive
• XML is a W3C Recommendation

Difference Between XML and HTML
 XML was designed to transport and store data, with focus on what data is
 HTML was designed to display data, with focus on how data looks
*HTML is about displaying information, while XML is about carrying information.

XML Does Not DO Anything!!
 Eg:-
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
- It has sender and receiver information
- This XML document does not DO anything -- information wrapped in tags.

Our Own Tags
• XML allows the author to define his/her own tags and his/her own document
structure.
• Eg:- <to> and <from> in above example.
XML is Not a Replacement for HTML
• XML is a software- and hardware-independent tool for carrying information.
• XML is used to transport data, while HTML is used to format and display the
data.

W3C Recommendation
 XML became a W3C Recommendation on February 10, 1998.
• XML is now as important for the Web as HTML was to the foundation
of the Web.
• XML is the most common tool for data transmissions between all sorts
of applications.

XML Separates Data from HTML
• to display dynamic data in your HTML document, it will take a lot of work to edit
the HTML each time the data changes.
• With XML, data can be stored in separate XML files.
 XML Simplifies Data Sharing
• XML data is stored in plain text format. This provides a software- and hardware-
independent way of storing data
 XML Simplifies Data Transport
• One of the most time-consuming challenges for developers is to exchange data
between incompatible systems over the Internet.
• Exchanging data as XML greatly reduces this complexity

XML Simplifies Platform Changes
• Upgrading to new systems (hardware or software platforms), is always time
consuming and large amounts of data must be converted and incompatible data is
often lost..
• XML data is stored in text format. This makes it easier to expand or upgrade to
new operating systems, new applications, or new browsers, without losing data.
 XML Makes Your Data More Available
• Different applications can access your data, not only in HTML pages, but also from
XML data sources.
 XML is Used to Create New Internet Languages
• XHTML
• WSDL for describing available web services
• WAP and WML as markup languages for handheld devices
• RSS languages for news feeds
• RDF and OWL for describing resources and ontology
• SMIL for describing multimedia for the web

XML Tree
• XML documents form a tree structure that starts at "the root" and branches to
"the leaves".
 Eg: <?xml version="1.0" encoding="ISO-8859-1"?>
<note>
<to>Tove</to>
<from>Jani</from>
</note>
- first line defines the XML version (1.0) and the encoding used (ISO-8859-1 = Latin-
1/West European character set).
- The next line describes the root element of the document
- The next 4 lines describe 4 child elements of the root
- finally the last line defines the end of the root element

Example:
• <bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
</book>
<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
</book>
</bookstore>
• The root element in the example is <bookstore>. All <book> elements in the document are
contained within <bookstore>.
• The <book> element has 4 children: <title>,< author>, <year>, <price>.

XML Syntax Rules
 All XML Elements Must Have a Closing Tag
This is a paragraph.
 
This is a paragraph.
 
• Note: You might have noticed from the previous example that the XML declaration
did not have a closing tag. This is not an error. The declaration is not a part of the
XML document itself, and it has no closing tag.
 XML Tags are Case Sensitive
• The tag <Letter> is different from the tag <letter>
 XML Elements Must be Properly Nested
• This text is bold and italic
 XML Documents Must Have a Root Element
• <root>
<child>
<subchild>.....</subchild>
</child>
</root>

• XML attribute values must be quoted
• Eg: <note date="12/11/2007">
<to>Tove</to>
<from>Jani</from>
</note>
• Entity References
<message>if salary < 1000 then</message>
<message>if salary < 1000 then</message>
< < less than
> > greater than
& & ampersand
' ' apostrophe
" " quotation mark

Comments in XML
• similar to that of HTML
- 
White-space is Preserved in XML
HTML:Hello Tove
Output:Hello Tove
• With XML, the white-space in a document is not truncated.
XML Stores New Line as LF
• In Windows applications, a new line is normally stored as a pair of characters:
carriage return (CR) and line feed (LF)
• XML stores a new line as LF.

XML Elements
• An XML element is everything from the element's start tag to the element's end
tag.
An element can contain:
• other elements
• text
• attributes
• or a mix of all of the above
XML Naming Rules
• Names can contain letters, numbers, and other characters
• Names cannot start with a number or punctuation character
• Names cannot start with the letters xml (or XML, or Xml, etc)
• Names cannot contain spaces

Best Naming Practices
• Make names descriptive. Names with an underscore separator are nice:
<first_name>
• Names should be short and simple
• Avoid "-" characters
• Avoid "." characters
• Avoid ":" characters

XML Elements are Extensible
• XML elements can be extended to carry more information.
XML Attributes
• Attributes provide additional information about an element.
Eg: <img src="computer.gif">
<a href="demo.asp">
• Attribute values must always be quoted
Eg:<person sex="female">

XML Elements vs. Attributes
Attribute:
• <note date="10/01/2008">
<to>Tove</to>
<from>Jani</from>
</note>
Element:
• <note>
<date>10/01/2008</date>
<to>Tove</to>
<from>Jani</from>
</note>

Problems with Attributes
• attributes cannot contain multiple values (elements can)
• attributes cannot contain tree structures (elements can)
• attributes are not easily expandable (for future changes)

XML Validation
• XML validated against a DTD is "Valid" XML.
• DTD is Document Type Definition (DTD)
Eg:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE note SYSTEM "Note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
</note>
• The DOCTYPE declaration in the example above, is a reference to an external DTD
file

Uses of XML
• Web publishing
• Web searching and automating Web tasks
• General applications
• e-business applications

Xml

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